The present invention relates to devices for presetting torsional tension on a shaft or tube. More particularly, the present invention relates to devices for setting the torsional tension on a tube supporting a cleaning blade for a conveyor belt cleaner.
Conveyor belts are frequently used to carry materials such as coal and aggregates that leave residues on the belts. These residues are frequently removed using scraper blades. The scraper blades must contact the belt with sufficient force to remove the residues, but excessive force results in excessive wear on the blades. Even when the force is properly adjusted, normal wear causes the contact force to fall out of the optimum range, requiring readjustment. When the blade is rigidly mounted the required readjustment frequency is greater than desired.
Gordon, U.S. Pat. No. 4,533,036, teaches a torsion bias mechanism that provides effective continuing compensation for wear along the line of contact between the scraper blades and the surface of the belt. Adjustment of the torsional force is achieved using adjacent collars, each with a series of radial apertures, and U-shaped links joining the collars in the desired angular relationship.
Mott, U.S. Pat. No. 5,201,402, sought to improve the mechanism of Gordon by providing greater precision in the mechanism for selecting the blade force. According to Mott, practical design considerations limit the precision of the incremental adjustments in the prior art devices to approximately 11.25 degrees of rotation. Mott taught axial hole patterns in adjacent collars to achieve an adjustment precision as fine as 1.5 degrees. Although finer precision settings are achieved, Mott's mechanism still only allows discrete torsional load settings. Furthermore, Mott's mechanism appears to require two people to set the tension. One tool must be inserted in the adjustment collar and one tool must be inserted in the tensioning collar. The two tools must be used in combination to set the desired tension and align radial holes on the collars to receive a locking pin.